Highly dense and highly dynamic Mobile Ad Hoc Networks (MANET) often have limited bandwidth available for the measurement and control of link performance parameters. Often, a receiving node can only measure and return link performance parameters to the transmitting node at a rate that constitutes a highly undersampled closed loop control loop with respect to the link dynamics encountered. Undersampling or the need for large control bandwidth to allow for adequate sampling is the bane of many MANET closed loop control methods. Open loop methods, where adjustments in transmission parameters for the forward link (node 1 transmitting to node 2) are made by node 1 based directly on receptions made on the reverse link (node 2 transmitting to node 1), can suffer from asymmetrical channel conditions.
Accordingly, there is a need to exploit the synergistic relationship between Open and Closed loop link measurements. More particularly, there is a need to utilize the Closed Loop more in static environments where a lower update rate may be acceptable since the channel is not as dynamic and where static asymmetric channel conditions can be compensated for via the closed loop. In dynamic channel conditions, the Open Loop may be favored since the asymmetrical channel fading can be filtered via low pass filtering and the more symmetrical link components compensated for, and where the Open Loop can provide lower latency in the link measurements with respect to the Closed Loop.
Further, there is a need to utilize pre-loaded State Transition tables that utilize the measurements made from either the Open or Closed loops as “trip points” between states. Since channel estimation can be a highly non-linear process, any algorithm used would be very segmented, by necessity, in order to approach piece-wise linear operation. The utilization of a State Transition table provides an optimal form of this piece-wise process whereas each state within the table may represent an optimal set of transmission parameters for the current link condition. Additionally, there is a need for methods in which the output from both the Open/Closed loop selection/combining process and the State Transition Transmission Parameter adjustments are used to estimate actual link quality in terms of stability, capacity, margin, or packet error rate.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.